Lighting system



July 27, 1943. v. l.. MALLoFYV 2,325,258

LIGHTING SYSTEM Filed Jan. 9, 1939 '7 Sheets-Sheet l NNN July 27, 1943. v. L. MALLoRY LIGHTING SYSTEM Filed Jan. 9, 1939 '7 Sheets-Sheet 2 wil v I/'z'non L. Maf/021g- July 27, 1943.

v. L. j MALLoRY LIGHTING SYSTEM Filed Jan. 9, 1939 '7 Sheets-Sh eet 5 AMPLIFIER POWE'I? SUPP/ Y zwan L. d

July 27, 1943.

V.v l.. MALLoRY LIGHTING SYSTEM sheets-sheet 4 Filed Jap. 9, 193s July 27, 1943. v. L. MALLORY 2,325,258

LIGHTING SYSTEM Filed Jan. 9, 1939 7 Sheets-Sheet 5 July 27, 1943. v. l.. MALLORY LGHTING SYSTEMl I Filed Jan, 9,' 1959 '7 Sheets-Sheet 6 July Z7, 1943- v. L. MALLoY LIGHTING SYSTEM Filed Jan. 9, 1939 7 Sheets-Sheet 7 Patented July 27, 1943 2,325,258 LIGHTING SYSTEM Vernon L. Mallory, San Antonio, Tex., assigner of A seventy per cent to Selden S. Nye, Brownsville,

Tex.

Application January 9, 1939, Serial No. 250,075

2 Claims. (Cl. 175-352) This invention relates to an improved lighting system and seeks, as one of its principal objects, to provide a system of this character more particularly intended for use with airports and other aircraft landing ilelds, which will be operable from an airplane for turning on flood lights or boundary lights, or both, on said landing neld, so that the services of an attendant may be dispensed with.

Another object of the invention is to provide a lighting system which, in one embodiment, will be set in operation by the sound of an airplane flying over apparatus employed.

Another object of the invention is to provide a lighting system which will be responsive to sound emanating from but one direction, so that it will not be placed in operation by thunder or` other sources of non-directional sound.

As a further object, the invention contemplates a lighting system which, in a second emtrolled selector employed.

Another object is to provide, in a lighting system, a selector which will be operative for indicating wind direction and variation so that if the wind changes direction while the pilot is landing the plane, he may change his course as may be necessary.

As a still further object, the invention provides Referring now tothe drawings forming a part oi' my application:

Figure 1 is a diagrammatic view showing my lighting system complete.

Figure 2 is a diagrammatic view of the photocell and amplifying unit therefor.

Figure 3 is a diagrammatic view of one of the audio-impulse amplifying umts, with` its power supply.

Figure 4 is a diagrammatic view, a portion of the apparatus being shown in elevation, of the automatic cut-oil.' unit.

Figure 5 is a schematic view showing the location of the sound pick-up unit with respect to a hangar.

Figure 6 is a plan view oi the wind controlled selector mechanism.

Figure 7 is a detail vertical sectional view on the line 1-1 of Figure 6, looking in the direction indicated by the arrows.

Figure 8 is a horizontal sectional view on the line 8-8 of Figure 6,1ookingin the direction indicated by the arrows.

Figure 9 is a schematic view showing the identifying means suitably located, that is to say, on top of a hangar.

Figure 10 is a top plan view of the identifying means.

Figure 11 is a diagrammatic View showing the receiving units employed.

Figure 12 is a diagrammatic view showing a suitable transmitting apparatus for operation in conjunction with the receiving unit shown in Figure 11.

Reference is now had to the accompanying drawings, wherein similar numerals will be seen to designate like parts throughout the various views.

There will rst be described the embodiment of the invention wherein operation of the lighting system is achieved by the transmission and reception of sound impulses from an airplane to receiving apparatus adjacent a flying field. This embodiment of the invention is best seen in Figures 5, 9 and 10 of the drawings, wherein is disclosed a hangar I having a roof 2. The hangar may be of any conventional construction and it is, oi course, to be understood that the sound pick-up units, to be described hereinafter, may be mounted in any desired location. For the sake of convenience, however, one of ythe units is shown as mounted on the roof 2 of the hangar I. The other sound pick-up unit or units should be mounted in a hangar or other building, or in any other convenient location, a substantial distance away from the first unit, for reasons which will become apparent hereinafter.

As shown in Figure of the drawings, the pickup unit 3 includes a. casing 3a mounted inthe roof 2 of the hangar I. The casing may be of metal or any other suitable material and is provided with a drain pipe 4 for draining olI rain water entering the casing. Mounted in the casing 3a is a microphone, shown schematically at 5. The microphone is electrically connected with an audio-impulse amplifier unit shown at 8, in Figure 1. sign but, nevertheless, is illustrated in Figure 3 ofthe drawings. 'I'he unit comprises a coupling transformer 1 and connected therewith in cascade is a plurality of yacuum tubes 8, 9, I8 and Il. The amplifier unit 6 includes a duplex power source I2. As the circuit details of the amplier unit are conventional and may be varied to suit conditions, it is not thought necessary to describe them herein.

As heretofore stated, at least two of the pick-up units 3 are employed and they are spaced a substantial distance apart. That is to say, one of the units 3 may be placed at one end of the landing field or airport while the other may be placed at the opposite end thereof. Each of the pickup units is connected with an amplifier unit 6 and, if necessary, suitable pre-amplifiers may be interposed in the circuit between the pick-up units 3 and said ampliiler units 6 in order to give suflicient gain for proper input to said amplier units. At I3 is shown a dual output relay of the opposed coil type. The relay |3'includes a coil I4 which is electrically connected to the output of one of the amplifier units 6 and a coil I5 connected to the output of the other of said units 6. It will be understood that the audio-impulses set up by the motor of an airplane ilying over one of the pick-up units will be converted into electrical impulses and amplifled to the extent that one of the relay coils I4 or I5 will be energized. Contacts, to be described in detail hereinafter, will be closed by the energization oi one or the other of the coils I4 and I5. Should a nondirectional audio disturbance, such for instance as a roll of thunder, take place, both of the pickup units 3 will receive a like amount of audioimpulses and the amplifier units 6 will both be operated for energizing both the coils |4 and I5 simultaneously. Under such conditions, the coil I4 will oppose the coil I5 and closing of the contacts of the relay will not take place.

The relay includes an armature I6 and contact springs |1 and I8. For purposes of clarity, it is believed advisable to indicate the other relays and elements which take a prominent part in the operation of this invention. With this in view, a selector relay is shown generally at I9 and includes an armature having contacts 2| and 22 associated therewith. Maintaining contacts are shown at 23 and 2,4. Control relays 25 and 26 are employed. The relay 25 includes contacts 21, 28, 29 and 30 while the relay 26 has 'contacts 3|, 32, 33 and 34. A photo-cell unit operated relay has contacts 36,!31, 38 and 39 associated therewith. Selector switches 40 and 4| are connected with the relay 35 and will be described in more detail hereinafter. The photo-cell unit operated relay 35 is adapted to be operated by a photo-cell 42 including an amplifier 43 and a photo-cell pick-up 44. For automatically returning the system to inoperative position after a plane has landed` or flown from the field, as the case may be, an automatic cut- 'I'he amplifier unit is of conventional de-V oil! unit 45 is provided. 'Ihe unit 45 will be described in more detail hereinafter as will be the photo-cell unit 42.

At 46 is shown a wind operated selector switch which is operable for controlling current flow to magnetic switches 41, 48, 49, 56, 5I', 52, 53 and 64. Each of the magnetic switches has a set of maintaining contacts 55, the purpose of which will be hereinafter set forth. Contacts for operating the lights themselves are shown generally at 56 in each of the magnetic switches. Wiring to the lights will be conventional and need not be described. The magnetic switches 41 through 54 are operable for controlling electric current Yto flood lights while boundary lights are to be controlled by a magnetic switch 51. The switch 51 has maintaining contacts 58 and controlcontacts 59.,

A pair of electric current conductors are shown aty 60 and 6| and are connected with a suitable power-source.` The conductor 60 is connected 'through a manually'operated master switch 82 and through the automatic cut-off unit 45 to the armature I6. The conductor 6| is connected to one terminal of the coil of the control relay 25 by a conductor 63. The other terminal of the coil 251s connected with the contact 2| .of the selector relay I9 by a conductorv 64. The armature 20 of the selector relay I9 is connected with the contact I8 by means 'of a conductor 65. It will now be understood that, upon energization of either of the coils I4 or I5, the current from the current source flowing through the conductors 60 and 6| will be led to the coil of the control relay 25. It should be understood that the selector relay I9 is ie-energized and that the contacts 20 and 2| are engaged. The relay 25 will thus be energized for closing the contacts 29 and 36. Current will be led from the conduci tor 6| through a conductor 66 and through a conductor 61 to one terminal of the magnetic switchv 51. The other terminal of said switch 51 is connected by conductors 68 and 69 to the other power conductor 60. 'I'he switch 51 will thus be energized for lighting the boundary lights on the landing field. In order to maintain the energization of the switch 51, after the initial energization thereof, certain circuit connections are necessary for the contacts 58. One of the contacts 58 is connected with the conductor 61 by a conductor 10 While the other of said contacts 58 is connected with the conductor 1| which is, in turn, connected by a conductor 12 with the conductor 69. Closing of the contacts 58 will thus insure energization of the switch 51 after initial energization in the manner hereinbefore described.

In order to maintain energization of the control relay 25 after initial energization thereof, the contacts 21 and 28 are closed. These contacts are electrically connected through switches 13 and 14 with a conductor 15 connected with a con- ;lucir 16 which is a continuation of the conduc- Either the boundary lights, controlled by the magnet switch 51, or the ilood lights, controlled by the magnet switches 41 through'54, or both,

may be turned on by an approaching airplane in following manner:

If the plane were to y over both of the sound asasgas I When the control relay- 25 is energized for supf plying current to the switch 51, current will also be led to the selector relay I 9. The circuit to the relay I9 will be complete only after the relay I3 has been returned to normal inoperative position. The contacts 23 and 24 will close upon energization of the relay I9 for maintaining said relay energized. The contacts 20 and 22 are closed for transmitting the voltage to one terminal of the coil of the relay 26 for the next period of operation of one of the sound, pick-up units 3. A conductor 11 leads the current from the contact 22 through a conductor 16 to the terminal of the coil of said relay 26. The other terminal of the coil of the relay 26 is connected to the conductor 6I by means of a conductor 1li.v

The contacts 3| and 32 are closed upon energization of the relay 26 and serve to maintain said relay energized after initial energization. A conductor 80 leads current from the conductor 16 (60) to the contact 3I. Switches 8| and 82 y are manually'operable for energizing or de-energizing the relay 26. The contacts 33 and 34 are, of course, closed by energization of the relay 26. The contact 33 is connected by a conductor 83 with the conductor 19 and thus with the conductor 6I. The contact 34 is connected by a conductor 84 with'a conductor 85 which is connected to corresponding terminals of the magnetic switches 41 through 54. The other corresponding terminals of the switches 41 through 54 are each connected. to a. segment on the selector switch 46. In more "detail, a, conductor 86 connects the other corresponding terminal of the switch 41 with the segment 81 on the switch 46. A conductor 88 connects the other corresponding terminal of the switch 48 with a segment 89 on the switch 46. In like manner, the other corresponding terminals of the switches 49 throughv 54 are connected respectively by conductors 90, 9|, 92,93, 94 and 95 to segments 96, 91, 98, 99, and IOI.

The details of the switch are best seen in Figures 6, '1, and 8 of the drawings. A selector staff |02 is mounted in a bearing |03 on a base disc |04 which carries the segments 81, 89, and 96 through IOI. A selector arm is shown at I 05. The selector arm isof inverted L-shape and has a yoke |06 which receives a collector wheel |01 adapted to roll over the segments. A collector spring |08 is carried by the arm |05 and engages the wheel |01 for insuring proper contact.

A weather vane |09 is carried at the upper end of the stair |02 and is adapted to have a oW of wind i'mpinge against the feathered end thereof for shifting the vane, stafl` and selector arm. It should be understood that the segments Will be calibrated with the vane so that when the wind is blowing from a particular direction, certain flood lights will be illuminated to define a, runway which will indicate to the plane pilot the proper direction to land. That is to say, it is obviously important that the plane land against the wind. For this reason the landing field is provided with a plurality of runways and means are provided for lighting each runway individually by flood lights placed at the head of the runway. In my improved lighting system. the pr'oper runway for the safest landing is selected by the wind operated selector switch as heretofore described. The pilot Will understand that he should approach the lighted runway from behind the nood lights so that he win thus :and into the wind. By virtue loithe fact that the maintaining contacts 55 `are provided for each of the switches 41 through ,s'aid switches will a manner that should the be interlocked in such wind shift direction, th iirst runway selected by the switch`46 will remain lighted and addi- ,tional runways will be lighted as the switch vmoves in response -to wind blowing from'other This will have the effect of indicatthewind is variable in direcx l directions. ing to the pilotthat tion and thus blowing in a direction midwaybetween two lighted runways, in ,which case they pilot obviously should choose the longest runway.

In order thatanairplane pilot desiring to land his plane on a landing field equipped with my improved lighting system, the sound;pickup units, I provide a screen IIO, best seen in Figures 9 and 10 of Athe drawings. The screen is adapted to be mounted above the pick-up units and has mounted therebeneathV a sign III which may be of the neon gas type or of any other suitable construction. In the example, illustra-ted in Figure 10, the sign embodies large letters which may be seen by the pilot.

These letters may indicate the name or the inthe drawings, complete. y

of photo-electric cells arev shown connected, ink

itial of the town or location of the field. Thescreen IIO serves to protect the sign |I| and the sound pick-up units therebeneath from hail or other objects or precipitation. The sign may be energized from any suitable source. Moreover, the screen IIO can conveniently form a background for a vane so thatv the pilot may b`et-' ter see the direction in which the vane is pointed with respect to surrounding objects. The photoelectric cell pick-up unit 44 is located beneath the sign vII| and in the path ofthe .beams of light from said sign. While I have only shown one ofthe screens IIO, it should be understood that a screen is provided for each of the sound and photo-cell pick-up units and for each of the signs. As heretofore stated, it is only necessary that the pick-up units and signs be positioned so that they may be conveniently located by the pilots to permit them to ily in suicient proximity to the units and signs to elect proper functioning of the units.

The photo-cell unit 44 is shown in Figure 2 of That is to say, a pair series and with the voltage amplifier Which mag- I nies the impulses to the extent that they will operate the vrelay 35. It should be understood that the equipment may belocated a desired distance from the photo-electric cells and that preampliflers may be used where necessary. The

photo-electric cells are shown at |I2 and I I3 in Figure 2 of the drawings. The amplifier is shown at II4. A duplex power supply is shown at II5 and is connected with the amplifier in a conventional manner. As in the case ofthe audio-impulse amplifier, variations in certain arrangements are quite possible and, in fact, so frequent that only a typical circuit arrangement has been shown. The output of the amplier is led by conductors I I6 and I I1 to the magnet coil of the magnet 35. It will be readily understood that the usefulness of the system would be greatly curtailed should the sign or indicating light become inoperative, for the reason that the pilot might be unable to locate the pick-up units. Therefore, in the event'the sign III should not be illuminated, current owing through the photo-electric cells will be greatly reduced. 'I'his will result in Varying of the grid bias voltage in may properly identify the amplifier ||4. Consequently, increase in plate current of the output tube will result and the relay 35 will be energized.

Upon energization of the relay 35, the contacts 36 and 31 will be engaged as will be the contacts 38 and 38. The contacts 31 and 38 are connected by a common conductor |8 to the conductor 16. The conductor 36 is connected through the switch 40 and through the conductor 11 to the coil of the relay 26 while the conductor 39 is connected through the switch 4| to a conductor ||3 and the conductor 64 to the coil of the control relay 25. Therefore, if the switch 40 is closed, current Will flow from the current source through the conductors 60, 16, H8, through the contacts 38 and 31, through the switch 40, and conductor 11, to the control relay 28. The flood lights will be lighted for the runway connected by the selector switch 46 and the magnetic switch in circuit therewith, depending upon the direction of the wind. Should it be desired to light the boundary lights only or to light the boundary lights in addition to the ood lights, the switch 4| is closed. Current will then ilow from the conductor 16, in the manner previously described, through the conductor H6, through the contacts 38 and 39, through the switch 4|, through the conductor H9, through the conductor 64, and to the control relay 25. The magnetic switch will be energized to illuminate the boundary lights.

The description of the invention up to the present has related to the operation of the system by the sound of the motor of an airplane flying overhead. There will now be described that part of the system whereby a radio transmitter in the airplane will be operative for sending continuous electro-magnetic waves to pick-up units |50 and |5|,for selectively energizing the coils |52 and |53 of the magnet |54 The receiving and transmitting units are shown, respectively, in Figures 11 and 12 of the drawings. The units |50 and |5| are of conventional design and are preferably of the superheterodyne variety, as this type of receiver is more selective than other types known. The receivers are tuned to respond to different frequencies and, in order to cause operation of the magnet |54 connected with the receivers, it is necessary that the transmitted sig nal be on the frequency of one or the other of the receivers. It has been found that the use of two radio receiving sets is highly advantageous for the reason that, not only is it possible to operate the system by the use of either oi.' two different frequencies, but, also, the possibility of the system being operated by static is eliminated.

That is to say, the units and |5| are connected to the coils |52 and |53, which are of the opposed current type. Should an operating signal be received by one of the receivers, the coil connected therewith will be energized for operating the relay and thus the system. Should a burst of static or other interference be set up' in the atmosphere, both receiving units would be operated. Both of the coils 52 and |53 would be energized and would oppose each other so that the relay |54 would remain inoperative. Contacts |20 and |2|, and a conductor |22 connect the relay |54 with one of the units so that selective opertaion of the radio units will cause operation of the relay |3. The transmitter unit, shown generally at |55, is of any suitable design.

Let it be understood here that the radio equipment now in use in a large number of airplanes could be used for this purpose with minor alterations. That is to say, if a cut-oifilter, designed to cut of! all frequencies above 2,000 cycles. be inserted in the audio circuit of the transmitter, and. likewise a filter of the same nature be inserted in the communications receiver, then regular communication could be maintained without operating the lighting equipment, providing that the receivers that operate the lighting equipment have a band-pass iilter designed to pass some frequency above 2,000 cycles, for example, 5,000 cycles. Then when a 5,000 cycle signal is modulated on the transmitter it will operate the lighting equipment Without being heard on the communications receiver.

There will now be described the cut-ofi un employed. That is to say, in the event the pilot of an airplane, after causing the plane to actuate thc system, should decide not to land, or in the event that the plane should land, the lights of the field would be automatically cut oil by this cut-ofi' unit unless previously extinguished manually by the master switch 62 or by certain of the other switches. The cut-oir unit is shown generally at 45 in Figure l of the drawings, and is shown in detail in Figure 4. The cut-oil unit includes input terminals |25 and |26 which are adapted to be connected either with terminals |21 and |28 of the control relay 25, or terminals |28 and |30 of the control relay 26. If desired, a double throw switch may be employed for selecting either of the relays 25 or 26 to be connected with the cut-oil unit. It will be noted that the terminals |21 and |28 and the terminals |29 and |30 are respectively connected across the control relays 25 and 26. If the time period 4for lighting the field is to run from the instant the boundary lights, controlled by the magnetic switch 51, are lighted, connection is made to the relay 25. Otherwise, connection is made to the coilof the relay 26, which will start the time period from the time the flood lights are lighted. In either event, a relay |3|, having contacts |32, |33, |34, and a second set of contacts |35 and |36, is energized from the relay 25 or the relay 26. vEnergization of the relay |3| will close the contacts |35 and |36 so that a relay |31 is energized and contacts |38 and |33 closed. The relay |31 is maintained energized so that, should current flowing to the relay |3| be interrupted, energization of the relay |31 will be maintained; Upon closing of the contacts |35 and |36 of the relay |3|, a motor |40, pivotally mounted on a frame |4|, is started, said motor being connected in parallel with the coil of the relay |31 by conductors |42` and |43. A cam shaft |44 is mounted on the frame |4| and is driven by semi-frictional rotating members |45 and |46. The cam shaft is supported at its opposite end portions by uprights |41 and |48 on .the frame. Mounted on the cam shaft |44 are cams |49 and |50. The cam |49 is adapted to open and close contacts |5| and |52 while the cam |50 is operable for opening and closing contacts |53 and |54. The contacts |5| and |52 are mounted on a disc |55 of insulating material rotatably mounted on the cam shaft |44. An upstanding stud |56 has a locking screw |51 screwed therethrough. The locking screw is operable for clamping the edge portion of the disc |55 against a stop iinger |58. It will be seen that the disc may be rotated to any desired position for varying the time required for the cam |43 'to open and close the contacts. On the cam shaft |44 is fixed a stopA asaaaus pin |59 which is engageable with a stop lug |60, for limiting rotative movement of the cam shaft. A coil spring |6| has one end secured to the shaft |44 and the other end secured to the base |4|. The spring |6| is operable for returning the cam shaft to a raised position after operation. A motor solenoid |62is energizable for shifting the motor out of frictional engagement with the cam shaft.

At |63 is shown a relay which has a coil |64 and con-tacts |65, |66, |61 and a second set of contacts |68, |69 and |10. Rotation of the cam |49 will close the contacts |5| and |52. The coil |64 and relay |63 are energized and maintained energized by the closing of the contacts |66 and |61. The contacts |68 and |69 are similarly connected by energization of the relay |63 so that the relay |31 is deenerglzed. The motor is stopped. Similarly, contacts |69 and` |10 are closed for energizing the solenoid |62 which shifts the motor and disengages the frictional connection between the members |45 and |46. The cam shaft |44 will be freed and the spring |6|, which has. been'wound during the period of rotation of the cam shaft, will return the shaft to normal position. The contacts and |52 will be opened but this action is of no consequence since the relay |63 has been maintained energized by closing of`the contacts |66 and |61. The contacts |53 and |54 will be opened, with the return of the shaft to normal position, by the cam |50.- This, in turn, opens a circuit so that the relay |63 is deenergized. The' relay |63, being de-energized, permits the solenoid |62 to become cie-energized so that the shaft of the driving motor is allowed to return to driving posi-tion. Y

At |1| is shown a fourth relay which is energized during the period of energization of the relay |63, due to the fact that the relay |1| is connected in parallel with said relay |63. The relay |1| has contacts |12 and |13 which are held open by energizatlon of the coil -of the relay |1|. During the period of 'time that the ,contacts |12 and |13 are held open, the circuit to the system through the conductors |14 and |16 is maintained inoperative.

'I'he purpose of the contacts |32 and |33 of the relay |3| will now be explained. Let it be assumed that the lcontrolled lights have been turned on either automatically or manually. The automatic cut-off unit is now in operation. Let it be assumed that the lights have been cut ci! manually which stops current now through the coil of the relay |3|. Upon de-energization of the relay |3l, the contacts |32 and |33 are closed and, being connected in parallel with the contacts |5| and |52, have the same effect as the closing of these latter mentioned contacts. The entire mechanism is thus returned to inoperative position. The source of current supply for operating the motor |40 and the various relays in the cut-ofi unit is led by conductors |16 and |11 from the conductors 60 and 6|. As the conductors themselves are of conventional design, it is not thought necessary to describe the connections in detail, the manner of 'connecting the various components having been set forth hereinbefore.

It is believed that the construction and operation of my improved lighting system will now be thoroughly understood. It will be readily seen that this lightingsystem may be used effectively on an emergency or other landing field where the usual lighting means are not available, by the use of automatic engine driven generators and storage batteries, the batteries being charged automatically periodically whenever needed. Further description of the invention is thought to be unnecessary.

Having thus described the invention, what is claimed is:

1. In a system of the class described, in combination with boundary lights and flood lights for an airport and'a source of audio 'frequency impulses, an impulse responsive unit responsive to uni-directional impulses and including a relay having a pair of coils connected so that energizing current will produce iields in opposite directions, a current source, a selector relay operatively connected with the iirst-mentioned relay and having contacts, a pair of control relays having contacts, said control relays being operatively connected with the selector relay, a magnetic switch for controlling current flow to the boundary lights, said switch being connected with one of the control relays, and a magnetic switch for controlling current iiow to the airport ilood lights, said switch being connected to the other of said control relays, said selector relay being initially energizable for connecting the first-mentioned control relay in the circuit whereby the firstmentloned magnetic switch will be operated for closing the circuit to the airport boundary lights, said selector relay being secondarily energizable for actuating the second-mentioned control relay for energizing the airport iiood lights.

2. In a system of the class described, in com-` bination with boundary lights and flood lights for an airport, and a source of audio frequency impulses, an impulse responsive unit responsive to uni-directional impulses and including a relay having a pair of coils connected so that ener-` gizing current will produce fields in opposite directions, a current source, a selector relay operatively connected with the iirst-mentioned relay and having contacts, a pair of control relays having contacts, said control relays being operatively connected with the selector relay, a magnetic switch for controlling current iiow to the boundary lights, said switch being connected with one of the control relays, a magnetic switch for controlling current to the airport iiood lights, said switch being connected to the other of said control relays, said selector relay being initially energizable for connecting the first-mentioned l control relay in the circuit whereby the iirst- VERNON L. MALLORY. 

